Metal-assisted chemical etching in HFÕH2O2 produces porous silicon

A simple and effective method is presented for producing light-emitting porous silicon ~PSi!. A thin (d,10 nm! layer of Au, Pt, or Au/Pd is deposited on the ~100! Si surface prior to immersion in a solution of HF and H2O2 . Depending on the type of metal deposited and Si doping type and doping level, PSi with different morphologies and light-emitting properties is produced. PSi production occurs on the time scale of seconds, without electrical current, in the dark, on both pand n-type Si. Thin metal coatings facilitate the etching in HF and H2O2 , and of the metals investigated, Pt yields the fastest etch rates and produces PSi with the most intense luminescence. A reaction scheme involving local coupling of redox reactions with the metal is proposed to explain the metal-assisted etching process. The observation that some metal remains on the PSi surface after etching raises the possibility of fabricating in situ PSi contacts. © 2000 American Institute of Physics. @S0003-6951~00!05542-X#